1. Field of the Invention
The present invention relates to a liquid-crystal display apparatus.
2. Description of the Related Art
In recent years, liquid crystal displays, which incorporate a liquid-crystal display panel, have been used as display apparatuses. Liquid crystal displays have found use in various electronic apparatuses, particularly in electronic pocket diaries, personal digital assistants (PDAs), cellular telephones, tablet personal computers (PCs), and notebook PCs and the like, which are light, thin and small and are hence portable.
In some cases, the information displayed on an electronic apparatus should not be accessible by any person other than the user of the apparatus. This situation takes place when, for example, a cellular telephone, a PDA or a tablet PC displays private information while the apparatus is being used in public. In view of this, the smaller the viewing angle, the better. It may also be desired, however, for the apparatus to have the function of controlling the viewing angle, because not only the user but also other persons may need to observe the image displayed on the apparatus. This question about the viewing angle is common to both portable apparatuses and public information terminals.
As disclosed in, for example, Jpn. Pat. Appln. No. 2003-58066, detachable louver sheets have recently come into use as a means for controlling the view angle of the liquid crystal display or the cathode-ray tube (CRT). Further, a system has been put to practical use in which the liquid crystal display used has no polarizing plates on the viewer side of a liquid crystal display. The user can observe the information only if he or she wears polarizing glasses.
The conventional louver sheet has a light-shielding layer, which is several millimeters wide in the normal direction of the sheet, in order to reduce the viewing angle sufficiently. Inevitably, the method using a louver sheet is disadvantageous since the louver sheet has low light transmittance. In addition, the method of manufacturing the louver sheet is complicated, which means the manufacturing cost of the louver sheet is high. Further, it takes much time to attach or detach the louver sheet. On the other hand, the method of using polarizing glasses is disadvantageous since the image cannot be seen by people without polarizing glasses. To solve the problem of lack of control over viewing-angle, a liquid crystal display with a viewing-angle controlling liquid-crystal panel was developed.
If a liquid crystal display has a viewing-angle controlling liquid crystal panel, however, the thickness and weight of the liquid crystal display will increase. Moreover, the use of the viewing-angle controlling liquid crystal panel will raise the manufacturing cost of the liquid crystal display, which will increase the price of the liquid crystal display.